Parallel systems employ a plurality of processors to perform tasks more quickly than would be possible with a single processor. Conventional software directing such systems breaks tasks into subtasks that can be more performed simultaneously. Parallel systems can also operate unconstrained by physical boundaries between hardware devices. For example, a parallel system can logically treat a single physical processor as two virtual processors by dividing the resources of the single processor between the two virtual entities. Virtual processors can also be allocated portions of the electronic storage capacity of the overall system in addition to a portion of the processing capacity. In such a system, if a task requires manipulation of specific data, the virtual processor that has been allocated the storage with that data is often the best choice for performing the task. Parallel system software conventionally includes substantial subportions dedicated to communications between the virtual processors.
The resources of some parallel systems are also organized on a higher level than the virtual processors. While the units of higher level organization can be given many different names, the term “nodes” will be used to discuss such units herein. Communication between virtual processors to achieve a task can entail communication between nodes when the virtual processors are associated with different nodes. Communication between the simultaneously active portions of a parallel system can become difficult when hardware or software problems cause a subset of the processing or storage resources to become unavailable. Communications can be established by repeating the procedure by which the system was initiated. During this re-initiation process, processing activity may be interrupted and progress that may have been achieved on tasks that the parallel system was addressing may be lost.